I'm afraid I don't know enough about CAD programming to make my own alterations - I wouldn't know where to begin. As far as the other differences go, I don't know that either. All I know is the hole spacing is narrower (21mm between centers), because when I bought my printed parts kit the seller accidentally put a dibond fan bracket in the kit instead of one for the sturdy and the slots in the bracket didn't line up with the mounting bolts. He sent me the correct one and it fit perfectly. I wanted to use your fan duct because I am using a J-head type hot end that uses a heater cartridge instead of a resistor (similar to the E3D) and therefore the corners of the larger heater/nozzle block touch the sides of the duct opening and burn and melt it. I'm hoping this one has a large enough opening to accommodate my hot end. Distance from the back of the fan bracket (where it contacts the X-carriage) to the center of the duct opening is 40mm. The original duct opening is about 23mm across (though mine is a bit melted so it's hard to be accurate).